Parallel piston engine



June 10, 1947. C, L, HQLMES PARALLEL PIsTN ENGINE Filed lay 8, 1944 3 Sheets-Sheet 1 MAL N m5 E N .r 10 e m @n L 1T \Ml H d NNJN m/ A5 .1 l 73M? .v E m i w m L UJ m 2W w ,im .NM u Q is M\ QN June l0, 1947. c. L.. HOLMES FRALLEL PISTON ENGINE 3 Sheets-Sheet 2 Filed llay 8, 1944 642,5 L HOLMES 74am, f4.9, faam TTOENEY'S June 10, 1947. C, HOLMES -2,421,884

Y PARALLEL PISTON ENGINE Filed May 8, 1944 3 Sheets-'Sheet 3 @.mw m

INVENTOR.

@H2L f'. HOLMES BY TTORNEYS Patented June 10, 19.47

OFFICE PARALLEL PIs'roN ENGINE Carl L. Holmes, Glendale, Calif. Application May 8, 1944, Serial No. 5034,607 .24 claims. (ci. 12s- 53) The present invention relates to improvements in a parallel piston engine, and it consists of the combinations, constructions and arrangements hereinafter described and claimed.

This invention is a simplication of the opposed piston engine shown in my copending application, Serial No. 530,246, filed April l0, 1944. The co-pending case relates to a two-cycle internal combustion engine of the compression type where one of the pistons trails the other. In the present case the opposed pistons rather than being in alignment with each other are arranged in parallel relation, both the working and the trailing pistons operating in cylinders that parallel each other and communicate at their tops. This arrangement does away withfthe auxiliary crankshaft that is needed for the trailing piston and permits the trailing piston to be connected directly to the main crankshaft. The change also eliminates the mechanism for operatively connecting the two crankshafts together.

In all other respects the present form of the invention operates on the same principle as the forms shown in my (zo-pending application. There has been a' slight change in the angle that the working crank arm assumes with respect to the cylinder axis when working and trailing pistons are at maximum compression. In the present form of the invention an angle of 20 is made between the working crank arm axis and the cylinder axis, whereas in the co-pending application the angle is 15.

A modified form of the invention is disclosed and in this form the trailing piston is made in the shape of a sleeve that encircles the work piston, both the sleeve and the piston being reciprocably mounted in the same cylinder. The area of the top of the trailing sleeve is designed to be approximately one third the area of the work piston top. The principle on which this modied form of engine operates is the same as -that disclosed in the preferred form.

Other objects and advantages will appear inthe following specification, and the novel features of the device will be particularly pointed out in the appended claims.

My invention is illustrated in the accompanying drawings forming a part of this application, in which Figure 1 is a transverse Vertical section taken through the engine, showing the power piston at the point of maximum compression;

Figure 2 is a vertical longitudinal section and shows the work and trailing pistons;

Figure 3 is a transverse section taken along 2 the line 3--3 of Figure 2 and ing piston Figures 4, 5, 6 and 7 are diagrammatic views showing the work and trailing pistons in difierent positions.

Figure 8 is a vertical transverse section through a modified form of engine; and

Figure 9 is a vertical longitudinal section taken along the line 9--9 of Figure 8. I

While I have shown only the preferred forms of my invention, it should be understood that various changes or modifications may be made within the scope of the appended claims .without departing from the spirit and scope of the invention.

In carrying out my invention, I provide an engine block indicated generally at A in Figure illustrates the traill. The engine block has a plurality of work cylinders I therein and a plurality of cylinders 2 for reciprocably receiving trailing pistons. In Figure 2 only one work cylinder and one trailing cylinder are illustrated although it should be borne in mind that any desired number of pairs of cylinders may be provided in one engine block. The work and trailing cylinders are arranged in pairs as clearly shown in Figure 2.

A crankshaft 3 is mounted in a crankcase bearing 4, which in turn, is supported by the crank case 5. At least two bearings will be provided for the crankshaft and additional gearings may be used if necessary. A work piston 6 is reciprocably mounted, in the cylinder I and is operatively connected to the crank arm 'I by a connecting rod 8. The trailing piston 9 is reciprocably mounted in the trailing cylinder 2 and is connected to a crank arm III of the same crankshaft 3 by a connecting rod I I.

Figure l illustrates the work piston at the instant of maximum compression and it wil1 be noted that the axis 0f the Work crank arm 'I makes an angle of 20 with the cylinder axis I2. The trailing crank arm I Il makes an angle of with the work crank arm 1, so that at the moment of maximum compression the axis of the trailing crank arm Iwill make an angle of 40 with the cylinder axis I2. It will be noted that the work crank arm 1 is longer than the trailing crank arm I0 but before going into the theory of the operating principle it is best to describe the other parts of the engine more in detail.

In Figure 2 I show the tops of the cylinders I and 2 communicating with each other in a common cylinder head I3 that overlies both cylinders. A spark plug I4 is placed in the cylinder head and an ignition system, not illustrated, may be used for causing a spark to ignite the compressed gases'l at the desired moment. The engine block A has fuel supply passages l5 encircling the trailing cylinder 2 and communicating with the cylinder through an annular ring of inlet ports i5. The trailing piston 9 acts as a valve and uncovers the inlet ports I6 at the proper moment 'which will be described hereinafter.

Exhaust passages il encircle the work cylinder I and communicate with the interior of the cylinder through exhaust ports i8. The work piston 6 acts as a valve for uncovering the exhaust ports at the proper time interval. A plurality or horizontally disposed iins i9 extend from the sides of the engine block for cooling purposes and -another group of vertically extending fins El: project above the top of the engine block.

Coming now to the principle or operation, it will be noted from Figure l that when the work and trailing pistons are at their maximum compression, the axes or the crank arms l and i will make angles of 20 and 40 respectively with the cylinder axis i2. The central pivot point, of connection between the connecting rod 8 and the crank arm 'I is indicated at 2i and this point will describe a circle indicated at 22. The central pivot point of connection between the connecting rod Ii and the crank arm I0 is indicated at 23 and this point describes a circle 2B. When the two pistons 6 and 9 are at their maximum compression, the points 2l and 23 will be disposed equidistant from the cylinder axis i2, see Figure l, as shown by the lines 25 and 26, which are of equal length.

The effective leverage of the two crank arms 1 and I0 at the moment of maximum compression will be equal. This is true because the sine of the angle 20 times the length of the power crank arm 1 equals the sine of the angle 40 times the length of the trailing crank arm i0. It should be noted at this point that although the effective leverage of the two crank arms is equal, a. greater force will be exerted against the work piston than against the trailing piston because the work piston is of a larger diameter than the trailing piston. It will further be noted thatl at the moment of greatest compression the work crank arm 1 has traveled 20 beyond top dead center and therefore further rotation of the crank arm will cause the work piston to descend rapidly because the swinging of the crank arm from 20 position to the 90 position, past top dead center, permits the work piston.to accelerate rapidly and therefore an explosion force delivered against the work piston will have its-greater energy expended in rotating the crankshaft 3 rather than being dissipated against a piston that is at top dead center.

While the work piston is moving rapidly downwardly during the ring stroke the trailing piston is moving upwardly from its crankshaft arm position of 40 in advance of top dead center up to a position where the trailing piston will be at top dead center. This arrangement causes the trailing piston to be moved upwardly at a decelerating speedi'as the trailing crank arm i0 moves from its position of 40 in advance of top dead center up to its position at top dead center and any explosive force exerted against the trailing piston 9 will have less effect to drive this piston backward because the piston is rapidly approaching top dead center and offers an ever increasing resistance which will reach its maximum when the trailing piston is at dead center.

It will therefore be seen that by disposing ,the

,the trailing piston as it moves upwardly because as already stated, this piston is nearing the top of its stroke and is moving much slower than the work piston and the changing leverage oilers far more resistance.

An advantage is derived in cranking the engine from the compression of the gases due to this particular arrangement of pistons and crank arm. For exampleduring the compression stroke the work piston is moved upwardly by its crank arm and since the trailing piston has its crank arm disposed 60 in back of the work crank arm, the trailing piston will not reach the top of its stroke simultaneously with the work piston. 'I'ne gases will be compressed by the work piston and some of them will flow into the top of the trailing cylinder. The work piston will reach top dead center and will start to move downwardly as the trailing piston is still moving upwardly to compress the gases in the trailing and work cylinders. Since the trailing piston is smaller in diameter than the work piston, the maximum compression can be realized with less effort expended in rotating the crankshaft than would otherwise be possible. The maximum compression takes place when the work crank arm has advanced 20 beyond top dead center and at this moment the firing of the compressed gases is accomplished. If desired a compression of the gases can be raised to a point where automatic ignition will take place because the compressed gases will reach a flash point temperature. This will do away with the need of a spark plug and will eliminate the ignition system. i

Although Figure 1 shows maximum compression with the work crank arm and the trailing crank arm making angles of 20 and 40 respectively, with the axis l2, it is obvious that s. change in the positions of the two crank arms may be eiected within proper limits. For example a satisfactory operating range for the work crank arm may be an angle from 10 to 25 past top dead center. A satisfactory range for the trailing crank arm I0 with the work crank arm 1 is an angle between 40 to 70. At most the angle must be less than The moment of ring, if accomplished by a. spark plug can be regulated to take place at maximum compression or a little in advance of maximum compression, this depending upon the Speed oi' the engine and the work to be performed.

In Figures 4 to '1 inclusive, I show various positions of the two crank arms and the two pistons to illustrate how the pistons act as valves for controlling the inlet and the exhaust of the gases. Figure 1 shows the pistons at the moment of maximum compression where the firing of the gases takes place. In thel transverse and longitudinal sections-shown in Figure 4, the trailing piston 9 is shown at top dead center with the power or work piston disposed 60 beyond top dead center or 40 past the optimum position of maximum compression. At this point all of the force oi' the exploding gases will be exerted on the working piston and the trailing piston acts asailxed wall.

In the transverse and longitudinal sections shown in Figure 5 the power piston 8 has moved 100- beyond the optimum position of 20 past top dead center. At this point the work piston starts to uncover the exhaust ports I6 and the trailing piston has moved 60 beyond top dead center. In Figure 6 the vpower piston has moved 205 beyond the vmaximum compression position shown in Figure 1 and now the exhaust ports are fully opened so that the exhaust gases will be expelled therethrough. The trailing piston starts to uncover the inlet ports and since the inlet gas will enter these ports under compression, the initial gas entering the trailing cylinder will now through this cylinder and into the work l cylinder to aid in scavanging or ilushing out the exhaust gases. In Figure 7 the power piston has traveled 250 from its maximum compression position and the exhaust ports are now closed. The trailing piston has closed the inlet ports and the two pistons are now ready to complete their compression strokes. The completion of the compression strokes is shown in Figure 1 and the entire cycle of operation strokes is also completed.

I have shown equal leverages of the crank shaft when the two pistons arel at maximum com-pression with the difference that a greater thrust is exerted on the work piston because of its greater size. Another way of setting forth the same matter is to state that when the work 'crank arm is 20 beyond top dead center, the

work piston has moved approximately through a little more than two percent of its full working stroke and the trailing piston is about fteen to eighteen percent short of the limit of its compression stroke. This is a'J ratio of about 1:8 measured in terms of proportion of working stroke traveled and the proportion of compression stroke yet to be traveled at the maximum compression positions.

In Figures 8 and 9 I show a modified form of the engine Where the work piston 25 and a trailing sleeve 26 are both mounted in the same cylinder 2l. The engine block B has inlet passages 28 communicating with the cylinder through inlet openings 29. The engine block also has exhaust passages 30 communicating with the cylinder through exhaust openings 3i. The trailing sleeve 26 has piston rings 32 that slidably contact with the enlarged upper portion 21a of the cylinder. The top area of the sleeve 26 together with the top surface of the uppermost piston ring 32 equals substantially, one third of the top area of the work piston 25.

Figure 8 shows the work piston 25 connected to a crankshaft 33 by'a connecting rod 34, the

rod being pivotally connected to a long crank arm 35. The trailing sleeve 26 has two lugs 36, see Figure 9, connected to eccentric rods 31 which in turn, are actuated by eccentric portions 38 formed integral on the crank shaft 33. Each eccentric portion has its center point 39 disposed a short distance from the axis of the crankshaft 33.

When the work piston and trailing sleeve are at maximum compression position, the axis o1' the crank arm 35 will make an angle of 10 with the vertical axis 40 of the cylinder. At the same time the center point 39 will be at a position where a line drawn 'from this point to the axis of the crankshaft 33, will make an angle of 40 with the vertical cylindrical axis 40. 'Ihe pivot point between the connecting rod 6 34 and the crank arm 351s shown at 4i and it will be seen that this point is spaced the same distance from the vertical line 40 as is the point Il when the work pistorr and trailing piston are at maximum compression. The leverage will be the same on both the crank arm 35 and the line 42 which is drawn from the point 39 to the axis of the crank shaft Il. However, a greater driving force will be delivered to the work piston because the top area of this piston is about two times more than the area of the trailing sleeve.`

The operation oi this form of the invention is the same as that shown and described in my preferred form. A spark plug 43 may be used or the compression Imay be arranged to provide flash point ignition. The various positions of the work piston and trailing sleeve throughout one complete cycle need not be given because they will be substantially the same as that given in the preferred form. The trailing sleeve has openings 4I which register with the exhaust openings 3| during the exhausting of thegases from the cylinder and from the interior of the trailing sleeve.

A modified form 4oi' engine can adapt it for a radial engine. The trailing pistons with the work pistons can be arranged in pairs around the engine axis. The trailing pistons are reciprocably connected by articulated rods to master connecting rods in the radial engine.

I claim:

1. In combination in a two-cycle internal combustion engine: a pair of parallelly arranged cylinders communicating with each other at their tops; a Work piston mounted in one cylinder and a trailing piston of a smaller diameter than the work piston mounted in the other cylinder; a common crank shaft for both pistons having a relatively long crank arm connected to the work piston and a relatively short crank arm connected to the trailing piston; the long crank being set relative to the short crank so that the working piston leads the trailing piston, and so that the leverages of the two cranks when their pistons are at positions of maximum compression are substantially equal;.the position of the crank of the working piston at maximum compression being about 20 degrees past top dead center; whereby an exploding of the gases of combustion at about maximum compression will cause a delivery of practically all of the power of the explosion to the work piston for rotating the shaft.

2. A combination according to claim 1 wherein the crank of the working piston has a lead of less than degrees over that of the trailing piston.

3. A combination according to claim 1 whereink the crank of the working piston has a lead of about 60 degrees over that of the trailing piston.

4. In combination in a two-cycle internal combustion engine: a work cylinder having exhaust ports therein; a second cylinder having intake ports therein; said cylinders communicating with each other at their tops; a work piston mounted in the work cylinder and acting as a valve for the exhaust ports; a, trailing piston mounted in the second cylinder`and acting as a valve for the intake ports; a common crank shaft for both pistons and having a relatively long crank arm connected to the work piston and a relatively short crank arm connected to the trailing piston; the lon-g crank being set relative to the short crank so that the Working piston leads the trailing piston and so that the leverages of the two cranks when their pistons are at positions of maximum compression are substantially equal; the position of the crank of the working piston at maximum compression being about 20 degrees past top dead center; whereby an exploding of the gases of combustion at about maximum compression will cause a delivery of practically all oi' the power of the explosion to the work piston for rotating the shaft.

5. In combination in a two-cycle internal combustion engine: a fpair of parallelly arranged cylinclers communicating with each other at their tops; a work piston mounted in one cylinder and a trailing piston of a smaller diameter than the work piston mounted in the other cylinder; a common crank shaft for bothvcpistons having a relatively long crank arm connected to the work piston and a relatively short crank arm connected to the trailing piston; the long crank being set relative to the short crank so that the working piston leads the trailing piston, and so that the leverages of the two cranks when their pistons are at positions of maximum compression are substantially equal; the position of the crank of the working` piston at'maximum compression being about 20 degrees past top dead center; a spark plug for exploding the gases of Combustion at about maximum compression for causing the gases to deliver practically all of their power to the work piston for rotating the shaft.

6. A combination according to claim 4 wherein the crank of the working piston has a lead of less than 90 degrees over that of the trailing piston.

7. A combination according to claim 4 wherein the crank of the working piston has a lead fof about 60 degrees over that of the trailing piston.

8. A combination according to claim 5 wherein the crank of the working piston has a lead of less than 90 degrees over that of the trailing piston.

9. A combination according 'to claim 5 wherein the crank of the working piston has a lead of about 60 degrees over that of the trailing piston.

10. In combination in a two cycle internal combustion engine: a pair of parallelly arranged cylinders communicating with each other at their tops to form a common combustion chamber, a work piston mounted in one cylinder and a trailing piston of a smaller diameter mounted in the other cylinder; a. common crank shaft for both pistons, having a relatively long crank arm operatively connected to the work piston and having its axis of rotation extending at right angles tc the cylinder axes; and a relatively short crank arm operatively connected to the trailing piston and having its axis of rotation extending at right angles to the cylinder axes; the long crank arm being set relative to the short crank arm so that the work piston leads the trailing piston and the two crank arms make angles with the cylinder axes so that when the pistons are at maximum compression, the sine of the angle that the long crank arm makes with the cylinder axis,

times the length of the long crank arm, is equal to the sine of the angle that the short crank ann makes with the cylinder axis, times the length of the short crank arm; whereby at maximum compression the two pistons are at the beginning ofthe power strike, the work piston having iinished its slower movement in passing top dead center and to accelerating on the power stroke; and the trailing piston having finished its faster movement and decelerating on its compression stroke as it approaches top dead center.

11. In combination in a two cycle internal combustion engine; a compartment for compressing gases of combustion therein; a work piston and a. trailing member reciprocably mounted in the compartment; a common crank shaft tor both the work piston and the trailing member having a relatively long crank arm operatively connected to the work piston and a relatively short crank arm operatively connected to the trailing member; the long crank arm being set relative to the short crank arm so that the work piston leads the trailing member and the two crank arms make angles with the compartment axis so that when the piston and trailing member are at maximum compression, the sine of the angle that the long crank arm makes with the axis times the length of the long crank arm is equal to the sine of the angle that the short crank arm makes with the axis times the length of the short crank arm; whereby at maximum compression the piston and trailing member are at the same elevation, the work piston-having finished its slower movement in passing top dead center and accelerating on the power stroke, and the trailing member having iinished its faster movement and decelerating on its compression stroke as it approaches top dead center.

12. A combination according to claim l wherein the position of the crank of the working piston at maximum compression is past dead center a distance less than 45.

13. In combination in a. two-cycle internal combustion engine; a cylinder; a sleeve slidably disposed in the cylinder; a work piston slidably mounted in the sleeve; both the tops of the sleeve and piston being adapted to compress a gas in the cylinder; a common crank shaft for both piston and sleeve; having a. relatively long crank arm connected to the piston and relatively short eccentrics connected to the sleeve; the long crank being set relative to the short eccentrics so that the piston leads the sleeve, and so that the leverages of the long crank and short eccentrics when the piston and sleeve are at maximum compression are substantially equal; the position of the crank of the piston when at maximum com pression lbeing about 10 degrees past top dead center; whereby an exploding of the gases of combustion in the cylinder at about maximum compression will cause a delivery of practically all of the power of the explosion on the piston to rotate the crank shaft.

14. A vcombination according to claim 13 wherein the crank of the piston has a lead of less than over that of the sleeve.

15. A combination according to claim 13 wherein the crank of the piston has a lead of about 50 over that of the sleeve.

16. In combination in a two-cycle internal combustion engine; a. cylinder having intake and exhaust ports therein; a sleeve slidably disposed inthe cylinder and having exhaust ports adapted to register with the cylinder exhaust ports at a certain period in the cycle; a work piston slidably mounted in the sleeve and acting as a valve for the sleeve exhaust ports; said sleeve having its top acting as a valvevtor 'the intake ports, the sleeve exhaust ports registering with the cylinder exhaust ports when the work piston uncovers the former ports; both the tops of the sleeve and piston being adapted to compress a gas in the cylinder; a common crank shaft for both piston and sleeve having a relatively long crank arm connected to the piston and relatively short eccentrics connected to the sleeve, the long crank being set relative to the short eccentrics so that the piston leads the sleeve and so that the leverages of the long crank and short eccentrica when the piston and sleeve are at maximum compression are substantially equal; the position of the crank of the piston when at maximum compression beingabout past top dead center; whereby an exploding of the gases of combustion in the cylinder will cause a delivery of practically all of the power of the explosion on the piston to rotate the crank shaft.

17. In combination in a two-.cycle internal combustion engine; a cylinder; a sleeve slidably disposed in the cylinder; a work piston slidably mounted in the sleeve; both the tops of the sleeve and piston adapted to compress a gas in the cylinder; a common crank shaft for both piston and sleeve; having a relatively long crank arm connected to the piston and relatively short eccentrics connected to the sleeve; the long crank being set relative to the short eccentrics so that the piston leads the sleeve, and so that the leverages of the long crank and short eccentrics when the piston and sleeve are at maximum compression are substantially equal; the position of the crank of the piston when at maximum compression being about 10 past top dead center;

` a spark plug for exploding the gases of combustion in the cylinder at about maximum compression for causing the gases to deliver practically all of their power to the piston for rotating the shaft.

18. A combination according to .claim 16 wherein the crank of the piston has a lead of less than 90 over that of the sleeve.

19. A combination according to claiml 16 wherein the crank of the piston has a lead of about 50 over that of the sleeve.

20. A combination according to claim 17 wherein the crank of the piston has a lead of less than 90 over that of the sleeve.

21. A combination according to claim 17 wherein the crank of the piston has a lead of about 50 over that of the sleeve.

22. In combination in an internal combustion engine; a pair of parallelly arranged cylinders communicating with each other at their tops to form a common combination chamber; a pair of opposed pistons operating in said cylinders, one of said pistons constituting a working piston and the other constituting a trailing piston; a relatively long crank operatively connected with said working piston; and a relatively short crank connected with said trailing piston for operating the latter, the long crank being set relative to the short crank so that the working piston leads the trailing piston, and such that the leverages of the two cranks are substantially equal when they are in their positions of maximum compression and the trailing piston after maximum compression will follow the working piston for a substantial portion of the power stroke.

23. In combination in a two-cycle internal combustion engine; a pair of parallelly arranged cylinders communicating with each other at arms and the velocity of the pistons are equal,

and subsequent to such position the velocity of the trailing piston is much slower than that of the working piston, the trailing piston then coming to rest at dead center and thus serving as a comparatively stationary wall to the exploded gases for a substantial portion of the power stroke.

24. A method of operating an internal combustion engine having a pair of parallelly arranged cylinders communicating with each other at their tops to form a common combustion chamber; and a pair of opposed pistons in said cylinders and having operating cranks, one piston constituting a Working piston and the other piston being a, trailing piston, said method comprising the steps of moving said pistons so that the Working piston'leads the trailing piston; causing said working piston to assume a position past top dead center when said pistons are at positions of maximum compression and causing said pistons to have substantially equal leverages in said positions; imparting substantially equal velocities to said pistons when .at said positions of maximum compression; moving the trailing piston toward its top dead center immediately following maximum compression, and simultaneously increasing the velocity of the working piston; and bringing the trailing piston to rest at its top dead center while moving the working piston at substantially its greatest velocity.

CARL L. HOLMES.

REFERENCES CITED The following references are of record in the tile of this patent:

UNITED STATES PATENTS Number' Name y Date 1,476,305 Toth Dec. 4, 1923 1,688,610 Burtnett Oct. 23, 1928 1,775,303 Baker Sept. 9, 1930 1,532,788 Vandervall Apr. 7, 1925 1,309,891 Grimth July 15, 1919 1,555,807 Burtnett Sept. 29, 1925 FOREIGN PATENTS Number Country Date 154,565 Great Britain 1921 704,528 France 1931 

